1. Field of the Invention
The present invention relates to a retractable lens system, more particularly to a retractable lens system including a radially-retractable optical element which is movable between a photographing position on an optical axis and a radially-retracted position eccentric from the optical axis.
2. Description of the Related Art
The assignee of the present invention has proposed a lens barrel retracting mechanism of a retractable zoom lens, which makes it possible to achieve a remarkable reduction in length of the retractable zoom lens when fully retracted, in U.S. patent application Ser. No. 10/368342. This lens barrel retracting mechanism has been incorporated in digital cameras commercially available under the trademark of “Optio S”.
The principal feature of the retractable zoom lens disclosed in the United States Patent Application is that an optical element of a zoom lens optical system is radially retracted from a position on a common optical axis of the zoom lens optical system to a different position outside of the optical axis, and the radially-retractable optical element and at least one optical element of the remaining optical element(s) of the zoom lens optical system are moved rearward along the optical axis when the retractable zoom lens is fully retracted, for the purpose of achieving a further reduction in length of the retractable zoom lens in a retracted state thereof.
More specifically, in this retractable zoom lens, a radially-retractable optical element (e.g., a lens group) is supported by a linearly movable frame which is guided linearly in an optical axis direction so that said radially-retractable optical element is capable of rotating about an axis parallel to the optical axis between a photographing position on the optical axis and a radially-retracted position (eccentric position), i.e., a position eccentric from the optical axis. This linearly movable frame is linearly moved in the optical axis direction by a torque of a rotating drive member between a retracted position and a ready-to-photograph position in the zooming range. A plurality of movable lens frames respectively supporting a plurality of lens groups which include the linearly movable frame are moved from their respective retracted positions to their ready-to-photograph positions in the zooming range by a rotation of a rotatable member rotated by the torque of the rotating drive member. Furthermore, the retractable zoom lens is provided with a stationary cam member which moves the aforementioned retracted optical element between the photographing position and the radially-retracted position thereof by a moving force of the linearly movable frame in the optical axis direction relative to the stationary cam member when the linearly movable frame moves from the retracted position to the ready-to-photograph position in the zooming range.
In this known retractable zoom lens, the space between the radially-retractable optical element and other optical elements at respective retracted positions thereof in the optical axis direction is minimized to reduce the length of the zoom lens in the retracted state thereof. However, subsequent investigation has revealed that there is still room for a further reduction in length of the zoom lens in the retracted state thereof.